As a conventional liquid ejection apparatus which ejects a liquid on to a target, there is, for example, an ink jet type printer which prints an image or the like by ejecting ink droplets on to a page. This type of printer has a carriage member having a recording head and a platen which supports a target, for example, paper. The recording head has a plurality of nozzles which eject inks. Paper is guided between the recording head and the platen and inks are ejected onto the paper from the nozzles. This printer is generally provided with a cleaning apparatus to clean the nozzles in order to prevent ink clogging in the nozzles. The cleaning apparatus includes a cap apparatus having a cap which covers the recording head, a tube pump to be connected to the cap apparatus and a wiping apparatus having a wiping member for cleanly wiping inks adhered to the recording head. The wiping apparatus wipes the recording head clean by causing the wiping member to slide in contact with the recording head.
The cleaning operation of the printer will be described in detail. First, after the carriage is moved to a position at which the recording head faces the cap apparatus, the recording head is covered tightly with the cap. Subsequently, the tube pump is driven to suck out the inks, which become highly viscous and may cause clogging in the nozzles, together with air inside the cap and discharge the inks outside the nozzles. While the tube pump is driven, the wiping member is placed at a predetermined position where the recording head can be wiped. When the suction of the tube pump is finished, the cap is moved downward after which the carriage is moved to cause the recording head to slide in contact with the wiping member, thereby wiping the recording head.
In such a cleaning apparatus, a drive source for driving the cap apparatus, the tube pump and the wiping apparatus is common for making the printer compact. As compared with the driving of the tube pump, however, the cap apparatus and the wiping apparatus are driven only for a short period of time and their timings differ. Therefore, the tube pump is constructed to be driven on the drive force directly received from the drive source, whereas the cap apparatus and the wiping apparatus are driven via a drive converting apparatus using part of the drive force from the drive source. (See, for example, Japanese Laid-Open Patent Publication No. 2000-153617 and Japanese Laid-Open Patent Publication No. 2002-225299.) Those publications disclose printers that use a drive converting apparatus which drives the tube pump and wiping member with a single motor.
In Japanese Laid-Open Patent Publication No. 2000-153617, for example, a pump wheel to drive the tube pump is arranged on one side of a gear to which the drive force of the motor is transmitted. As the gear rotates, the pump wheel rotates with the rotation of the motor to thereby drive the tube pump. Meanwhile, the wiping apparatus is arranged on the other side of the gear via a friction clutch as the drive converting apparatus. The drive force of the motor is transmitted to the wiping apparatus via the friction clutch, moving the wiping member to a predetermined position. The friction clutch is operated intermittently with respect to the driving of the tube pump.
In case of the publication described above, the drive force of the motor is transmitted to the wiping apparatus by the friction clutch alone. In the case where inks are adhered to a driven gear and the friction clutch, for example, the weights of the parts to be driven, i.e., the driven gear and the friction clutch, increase because of the adhered inks. Therefore, the frictional force needed to drive the wiping apparatus becomes greater so that even when the drive force of the motor is transmitted to the friction clutch, the wiping apparatus cannot be driven.
Japanese Laid-Open Patent Publication No. 2002-225299 discloses the printer which is provided with a drive shaft to drive the tube pump and the wiping apparatus. The drive shaft penetrates the center of the pump wheel of the tube pump. The tube pump is driven as the pump wheel is directly rotated according to the rotation of the drive shaft. The wiping apparatus has a first drive mechanism including a sun gear, a cleaner drive lever, a gear holding lever and a planetary gear which constitutes the drive converting apparatus, and a second drive mechanism different from the first drive mechanism. The drive shaft is fitted into the center of the sun gear. As the drive shaft rotates, the second drive mechanism is driven via the sun gear, positioning the wiper to a predetermined position. The first drive mechanism functions to intermittently operate the wiping apparatus with respect to the driving of the tube pump. Therefore, the drive converting apparatus in Japanese Laid-Open Patent Publication No. 2002-225299, unlike that in Japanese Laid-Open Patent Publication No. 2000-153617 can drive the wiping apparatus even if inks are adhered to those parts to be driven.
There was a case where printing defects would occur due to an increase in the viscosity of the ink caused by evaporation of a solvent, such as water, from the openings of the nozzles, adhesion of dust to the openings of the nozzles and mixing of bubbles in the ink caused by replacement of a cartridge, or the like.
To maintain the performance of the nozzles in the best condition, therefore, a nozzle protecting device equipped with the cap, which covers the nozzles of the recording head and the tube pump that sucks out ink, and bubbles or so in the cap covering the nozzles, is used. In the case where printing is not carried out over a long period of time, the nozzles are covered with the cap, thus preventing the ink from becoming dry. As needed, the tube pump is driven with the nozzles covered with the cap, setting the inside of the cap to a negative pressure, so that the ink whose viscosity is increased or bubbles or the like generated in the recording head by replacement or the like of the cartridge is discharged to the ink tank, thereby maintaining the performance of the nozzles in good condition.
If the tube pump is driven to set the inside of the cap to a negative pressure as mentioned above, the inks flow into the cap via the recording head and fill the inside of the cap. As those inks would become unnecessary at the time of performing printing, so-called air suction was performed to exhaust the inks into the ink tank by the tube pump while taking air inside the cap. Taking air inside the cap was executed while slightly separating the cap from the nozzles.
Recently, the sizes of ink jet type recording apparatuses (printers) are becoming rapidly smaller and demand for a greater degree of freedom for locating recording apparatuses is increasing. Recording devices are increasingly used in a state other than in a horizontal state, and if air suction is carried by the above-described method under such a usage, the inks would leak from the cap in the instant the cap is separated from the nozzles. As a result, the inside of the recording apparatus becomes dirty.
To ensure air suction even if the recording apparatus is placed in a state other than a horizontal state, therefore, air release means which causes the cap to communicate with air as needed while covering the nozzles is provided. The air release means can release the inside of the cap to air before the cap is separated from the nozzles, so that the inks can be exhausted outside without causing ink leakage.
One example of the nozzle protecting device having an air release means comprises a tube to communicate inside the cap with air and a valve which opens and closes the end portion of the tube. The nozzle protecting device is of a slide type whose slider elevates up and down as the carriage moves in the scan direction so that the cap covers the nozzles as it elevates according to the elevation of the slider. The opening/closing of the valve is executed according to the operation of the carriage in the scan direction and air is taken inside the cap as needed.
However, such air release means needs the tube suitable located and thus makes the structure of the nozzle protecting device complicated. Further, after the valve is opened or closed by the movement of the carriage, the inks inside the cap are exhausted by the tube pump. Therefore, the first drive means which drives the carriage and the second drive means which drives the tube pump should be driven separately, complicating the structure.
The slide type nozzle protecting device makes the space for the carriage in the scan direction larger, which is a factor to enlarge the device. Recently, therefore, an up/down movement type which can make the space smaller is becoming mainstream as compared with the slide type. For example, Japanese Laid-Open Patent Publication No. 2002-36578 discloses an up/down movement type nozzle protecting device provided with an air release valve.
The nozzle protecting device has a multi-stage rotary cam having a plurality of cams on the same shaft. The multi-stage rotary cam has a first cam to elevate the cap, a second cam to open and close an air communication valve as an air release means and a motor. As the drive force of the motor is transmitted to the multi-stage rotary cam and the gear of the tube pump, elevation of the cap, the opening/closing of the air communication valve and driving of the pump gear are carried out. And, the air communication valve is opened or closed with the cap covering the nozzles, after which the pump gear is driven to perform air suction.
The operations of the cap and the air communication valve have nothing to do with the movement of the carriage, and the cap, the air communication valve and the pump gear can be driven to perform air suction with a single motor, thereby simplifying the device.
While the nozzle protecting device disclosed in Japanese Laid-Open Patent Publication No. 2002-36578 is made simpler, however, it needs larger space for the multi-stage rotary cam so that the ink jet type recording apparatus is larger.
The drive converting apparatus disclosed in Japanese Laid-Open Patent Publication No. 2002-225299 is comprised of many parts. Accordingly, a heavy load is applied to the drive shaft that drives the wiping apparatus and the tube pump.
That is, a large drive force is needed to drive the wiping apparatus and the tube pump more reliably. Generation of large drive force requires the use of a larger motor. As size reduction of the drive converting apparatus, is eventually demanded together with size reduction of the recording apparatus, it will become difficult to use a large motor.
In the case where the target to be printed is a thick object, such as CD-ROM, it is necessary to make the distance from the platen to the recording head large. As the wiping apparatus is normally fixed to the printer, when the recording head is moved upward to make the distance from the platen to the recording head larger, the distance between the wiping member and the recording head changes. Accordingly, the slide pressure of the wiping member to the recording head changes, making it difficult to wipe the inks adhered to the recording head satisfactorily.
For example, Japanese Laid-Open Patent Publication No. 2002-264350 discloses a technique for reducing the wiping speed of the wiping apparatus or increasing the wiping ability of the wiping member to clean the recording head adequately even if the distance from the platen to the recording head is changed.
Even with the use of the technique disclosed in Japanese Laid-Open Patent Publication No. 2002-264350, however, it is difficult to sufficiently wipe and clean the recording head with the wiper when the distance from the platen to the recording head is changed. Therefore, there was a demand for a technique which would wipe and clean the recording head more satisfactorily with the wiping member even when the distance from the platen to the recording head is changed.